There are many prior art indexing arrangements for releasably fixing the angular relationship between a rotatably mounted spindle and a workpiece mounted on the spindle. In particular, conventional work-holding heads for mounting on a manually or hydraulically operated conventional grinding machine typically have an indexing plate provided on the spindle to permit releasably fixing the angular relationship of the spindle and hence the workpiece held on an end of the spindle to do particular grinding work on the workpiece.
However, in most machine shop applications and particularly in those applications involving grinding or re-grinding fluted tooling, (i.e. taps, hobs or other form-relieved tooling) a special fixture has been employed wherein a fixed, biased finger is mounted on or near the work head of the machine for engagement with the conventional circumferentially spaced recesses or teeth on the indexing wheel or plate connected to the spindle. In such operations, the operator is required to control the rotational feed of the workpiece into engagement with a grinding wheel relatively movable along the longitudinal axis of rotation of the workpiece for several passes until the necessary amount of material has been removed from the fluted cutting edge of the tool to restore the cutting edge and its original geometry.
Rotational feed control of the spindle in this particular arrangement is limited because the indexing plate is directly fixed to the spindle and by the nature of the indexing mechanism structure which relies upon movement of the biased indexing finger within a given indexing recess. This provides very limited rotation of the spindle in either direction while the finger is at least partially disposed within the recess. Rotational feed control in one direction is limited by the required engagement between the finger and indexing recess. Rotation in the opposing direction is limited to the position of the biased finger when it reaches the bottom of the indexing recess. This latter position prevents or blocks further rotation in that direction which essentially defines the fixed indexed relationship.
While there have been many attempts over several decades in the prior art to improve indexing function, such as providing greater flexibility in the number of angular rotational indexed positions provided, there has been a lack of a satisfactory device which provides positive indexing and rotational feed control while maintaining a fixed position between the indexing finger and the engaged circumferentially spaced recesses in a simple, efficient, and economical manner.